A vehicle provided with an ISG (Idle Stop & Go) system stops an engine when the vehicle stops and starts the vehicle when the vehicle restarts in order to reduce fuel consumption and emissions generation.
In further detail, the vehicle provided with the ISG system automatically stops the engine if idling is maintained for a predetermined time after the vehicle stops, and automatically restarts the engine if a brake pedal is released or an accelerator pedal is pushed.
Since a hydraulic pump (mechanical hydraulic pump) in an automatic transmission is not operated during an idle stop, hydraulic pressure is not generated in the automatic transmission in the vehicle provided with the ISG system.
If the hydraulic pressure is not generated in the automatic transmission, the hydraulic pressure cannot be supplied to friction members (clutches and brakes) operated at a first forward gear stage (gear stage at which starting control is performed) in a planetary gear set.
When a driver releases the brake pedal or pushes the accelerator pedal for restarting, the engine is automatically restarted and the hydraulic pump of the automatic transmission begins to operate to increase rotation speed of the drivetrain.
At this time, the hydraulic pressure in the automatic transmission rises quickly and then is supplied to the friction members, thereby achieving the first forward gear stage. Therefore, impact is applied to the vehicle, thereby causing displeasure of the driver and damage to the friction members.
In order to prevent such impact, a neutral state is temporarily achieved when restarting the engine. However, since the hydraulic pressure is supplied to the friction members for achieving the first forward gear stage after engine starting is performed at the neutral state and the hydraulic pressure is stabilized, a time delay to actually starting the vehicle may be long. Therefore, the hydraulic pressure is not, or is only partially, applied to the vehicle to achieve the neutral state only temporarily.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.